Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/18/17
Area Forecast Discussion
National Weather Service Taunton MA
938 PM EST Sun Dec 17 2017
.SYNOPSIS...
A weak wave of low pressure will bring a period of light snow
overnight into Monday morning, which may linger into the
afternoon across northeast Massachusetts. Temperatures will be
milder on Tuesday ahead of a cold front, then turn blustery and
colder Wednesday into Thursday but with dry weather prevailing.
Low pressure will likely pass to our west Friday night and
Saturday, probably bringing mainly rain and a period of rather
mild temperatures along with some wind. A period of unsettled
weather may return sometime Christmas Eve into Christmas, but
timing and precipitation types are uncertain.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
935 PM update...
Forecast on track. It will take several hours to moisten lower
levels given very dry air in place. Expect light snow to move
into western New Eng after midnight with any snowfall more
spotty as it reaches eastern MA toward daybreak. Only minor
temp drop overnight with increasing cloud cover.
Previous discussion...
Tonight into Monday morning...
***Light snow will likely impact the Monday morning commute***
Dry weather persists through late evening as mid level
cloudiness continues to thicken. Temps will generally range from
the teens to middle 20s through midnight.
Increasing potential for light snow showers to develop during
the overnight hours and move through southern New England during
the morning commute. Low pressure over the Great Lakes will
slowly begin to move towards the Northeast pushing the frontal
system to our south northward as a warm front. Ahead of the
front, isentropic lift within the WAA pattern will help provide
just enough lift for precip to occur. Increasing moisture in the
mid-levels will help saturate the snow growth region and with
soundings keeping the profile below 0C anticipate snow showers.
The lift does appear weak thus continued the mention of light
snow showers late tonight and into the morning hours.
One thing we will have to watch is the warm layer at 950mb. Both the
EC and HRRR are in agreement of thermals which keeps this warm layer
just south and west of our area, although it is close. Do not plan
on issuing any winter weather advisories at this time for CT or RI.
However with the cold temperatures overnight, any snow showers that
do occur will accumulate on the roadways just in time for the
morning commute. Will issue an SPS to highlight this concern for
tomorrow morning. Anyone traveling should take it slow as roads can
become slick. Overall snow accumulations will be around a coating to
less than an inch.
Snow should end by the mid-morning hours as the better lift moves
northward.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday afternoon into Monday night...
***Low chance for spotty freezing rain across Northeast
Massachusetts late Mon Afternoon***
Warm front to the south will begin to push into southern New England
during the day on Monday. Despite southerly winds at the surface, 2m
Temps from Hi-res guidance suggest that the front will struggle to
push through keeping many sites in the low to mid 30s. May see some
warming on the south coast to near 40F but it will be a struggle.
Any lingering precip from the morning hours will be spotty and very
light as the better lift continues to remain north of the region.
However profile is still quite saturated so any forcing could help
result in some showers. Depending on surface temps this could be
snow or rain. Precip chance for the afternoon into the evening will
linger across northeast MA as meso-low moving into coastal ME seems
to develop some sort of inverted trough over that region. With this
lingering moisture combined with increase 950mb warm layer, could
see some freezing rain by later afternoon into evening hours. This
could result in impacts to the evening commute in northeast MA. This
is shown in BUFKIT soundings especially for BVY, LWM and BED. It will
be close for BOS. Confidence is to low, and precip could be quite
spotty so will hold off on winter weather adv for now. Something the
overnight shift may want to look at.
Shower chances decreases by the late evening resulting in a dry
forecast for Monday night. Temperatures will remain steady as weak
warm front pushes northward.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...
* Much milder Tue with mainly dry weather
* Turning blustery and colder Wed into Thu with dry weather
* Mainly rain Fri night/Sat with some wind and mild temps favored
* Unsettled weather possible sometime Christmas Eve into Christmas
Details...
Tuesday...
Much milder weather expected on Tuesday with 850T near 0C and
southwest flow ahead of a cold front. High temps should reach into
the upper 40s to near 50 with even some lower 50s possible in the
coastal plain. Dry weather anticipated with the lack of synoptic
scale forcing, but can not rule out a spot shower or two toward
evening in western MA.
Tuesday night and Wednesday...
A cold front crosses the region region Tue night into early Wed with
colder/blustery weather to follow. Mainly dry weather anticipated
other than perhaps a few brief rain/snow showers across the east
slopes of the Berkshires. Increasing wind will keep low temps Tue
night mainly in the upper 20s to the lower 30s. High temps on Wed
will generally be in the 30s to around 40, but northwest wind gusts
of 25 to 40 mph will make it feel colder.
Wednesday night and Thursday...
Canadian high pressure builds into the region bringing dry but cold
weather. Low temps Wed night should mainly be in the teens, but
some single digits can not be ruled out in the normally coldest
outlying locations. High temps on Thu should mainly be in the
30 to 35 degree range, but with less wind than on Wed.
Friday and Saturday...
Upper level ridging will be building across the southeast states as
a shortwave trough lifts northeast towards the Great Lakes. While
it is too early to completely lock in a solution...the given pattern
and ensemble guidance strongly favors low pressure passing to our
northwest putting us on the mild side of the storm. Timing still
uncertain, but most guidance keeps the daytime hours dry with bulk
of the rain Friday night and/or Saturday. Now there initially is
still Canadian High pressure which slides off to the east, so can
not rule out the low risk for a bit of snow/ice at the onset
across the interior. Regardless, mainly rain is favored Friday
night into Saturday across the entire region. In fact, temps
could climb well into the 50s to near 60 for a time along with a
period of strong southerly winds.
Christmas Eve into Christmas...
Very low confidence forecast in this time range. Upper level ridge
with abnormally high height fields will be anchored off the
southeast coast. Meanwhile, a dome of arctic air and well below
normal temperatures will be invading much of the central states.
This will place our region in the battle ground between these
extreme airmasses. A couple waves of low pressure will likely track
along the baroclinic zone and bring the risk for a period or two of
precipitation sometime Christmas Eve into Christmas. Timing/ptypes
and will depend on exactly where the baroclinic zone aligns. While
snow is certainly an option especially at this time range...given
strength of southeast upper level ridge would favor rain/ice. If we
do have enough cold air for wintry precipitation, it might end up
coming down shallow given rather high height fields which could
possibly result in more of an ice threat than snow.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Monday Night/...High confidence.
Tonight...VFR with gradually lowering cigs through midnight.
Mainly MVFR conditions overspread western MA/northern CT in
light snow between 6z and 9z. These conditions may reach eastern
MA and RI towards 12z.
Monday...Widespread MVFR cigs with a few spots lowering IFR.
Chance of light snow north of the Pike and rain south of the
Pike. Precip will wind down by the afternoon. Lingering showers
in Northeast MA could result in a wintry mix resulting in slick
runways.
Monday night...Improving conditions to VFR during the overnight.
KBOS Terminal...Moderate confidence. Spotty light snow showers
may arrive towards 12z and persist at times into the late
Monday morning hours. May have to watch for spotty -fzdz after
20z. Low confidence if this will occur.
KBDL Terminal...High confidence. Light snow will likely impact
the terminal mainly between 6z and 10z Monday morning.
Outlook /Tuesday through Friday/...
Tuesday: Mainly VFR, with local MVFR possible. Windy with gusts
to 30 kt.
Tuesday Night: Mainly VFR, with local MVFR possible. Windy with
gusts to 35 kt.
Wednesday: VFR. Windy with gusts to 35 kt.
Wednesday Night through Thursday: VFR. Breezy.
Thursday Night: VFR.
Friday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Monday Night/...High confidence.
Tonight...Light winds and seas.
Monday...Winds becoming SW and increasing in the afternoon but
gusts below 20 kt. Seas below SCA. Chance of light snow changing
to rain.
Monday night...Dry weather with increasing winds and seas.
Conditions remain below SCA.
Outlook /Tuesday through Friday/...
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Local rough seas.
Tuesday Night: Moderate risk for gale force winds with gusts up
to 35 kt. Areas of rough seas.
Wednesday: Low risk for gale force winds with gusts up to
35 kt. Areas of rough seas.
Wednesday Night: Moderate risk for Small Craft Advisory winds
with areas of gusts up to 30 kt. Local rough seas.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft.
Thursday Night: Winds less than 25 kt.
Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Frank/Dunten
NEAR TERM...KJC/Frank/Dunten
SHORT TERM...Dunten
LONG TERM...Frank
AVIATION...Frank/Dunten
MARINE...Frank/Dunten
Area Forecast Discussion
National Weather Service Columbia SC
1052 PM EST Sun Dec 17 2017
.SYNOPSIS...
High pressure will shift off the Carolina coast overnight.
There will be increased moisture in the southerly flow on the
backside of the offshore high Monday. Additional rain chances
throughout the week expected with a weak front across the area.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Latest regional radar loop showing precipitation has become
quite spotty across the region with mainly only sprinkles out
there as the isentropic lift has weakened. Despite the best
moisture transport over the area currently, precipitable water
values will be lowering through the remainder of the night. Most
recent HRRR run showing little additional significant
reflectivity returns overnight, just continued isolated
sprinkles and possibly a shower or two mainly in the CSRA. Have
adjusted hourly grids to account for this and also adjusted
temperatures as observations are running a few degrees warmer
than forecast.
Widespread and increasing clouds should limit radiational
cooling this evening and overnight so expecting much warmer min
temperatures tonight compared to last night with lows in the mid
40s to low 50s.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
An upper level disturbance falls apart as it moves into the mean
ridge axis over the Southeast U.S. A very dry antecedent
airmass over the Carolinas will also inhibit chances of
precipitation with this disturbance.
A second stronger upper level trough is forecast to impact the
region starting on Wednesday. A warm front should be located near
the North Carolina/South Carolina border with overrunning rain.
Temperatures will be well above normal south of the front.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A strong disturbance moves off the Carolina coast Wednesday Night
with overrunning rain coming to an end. High pressure aloft rebuilds
Thursday into Friday with dry weather and well above normal
temperatures.
A cold front is forecast to sweep into the region this weekend with
a deep and broad upper trough across much of the U.S. next weekend.
The surface front may become parallel to the upper flow and stall
somewhere near the region early next week.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
VFR conditions through the early morning hours...then
restrictions expected through the end of the period.
Clouds have continued thickening and lowering over the past
couple of hours with regional radar showings only a few widely
scattered showers. With additional moisture moving into the
region overnight cigs expected to become MVFR at AGS/DNL around
06z and remaining terminals around 10z. Chance of rain remains
too low to include through 15z...then have included VCSH for
AGS/DNL/OGB with VCSH for CAE/CUB beginning 18z. For threat
overnight remains low...however have included for AGS during the
early morning and sunrise hours. Winds through the period will
be southwesterly at 5 knots or less.
EXTENDED AVIATION OUTLOOK...Boundary will remain stalled across
the region with rain and associated restrictions at times
through Wednesday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Forks ND
646 PM CST Sun Dec 17 2017
.UPDATE...
Issued at 629 PM CST Sun Dec 17 2017
Fog and low stratus deck the main concern and impact this evening
and overnight. Lowest visibilities so far at Crookston METAR
showing a half mile. Will continue to monitor its evolution and
coverage. Dense fog advisory a definite possibility this
evening, will see how observations do over the next couple hours.
&&
.SHORT TERM...(This evening through Monday)
Issued at 200 PM CST Sun Dec 17 2017
Concerns will be fog potential tonight and then snow chances on
Monday. 12z guidance in good agreement.
Lots of questions regarding clouds and fog potential for tonight.
Clouds and fog remain this afternoon where SFC dewpoint values
are in the upper 20s/low 30s. Latest RAP guidance indicates this
low level moisture will remain in place, and advect northward this
evening, placed along and east of the valley. With this thinking
in mind, will go mostly cloudy with fog east of the valley. Not
sure about dense fog potential but will monitor into the evening
hours. Anticipate high clouds overtaking the region by 12z Mon.
Warm air advection overnight will make min temp forecast tricky.
Steady temps along with clouds. Areas with no clouds this evening
will likely see a quick temperature drop before steadying and
possibly slowly rising. How far these temps fall is uncertain.
Left exit region of a strong upper level jet brings forcing and
snow chances to the northern half of the region on Monday.
Increase these snow chances based on the latest guidance. Most
guidance also indicating weak MUCAPE (up to 50 J/KG). Given the
forcing along with the potential for weak instability, convective
type snow showers could lead to a quick 2-4 inches on Monday. Main
message is for widespread snowfall totals of 1-2 inches with
localized snowfall up to 4 inches possible.
.LONG TERM...(Tuesday through Sunday)
Issued at 200 PM CST Sun Dec 17 2017
A sfc ridge builds into the area on Tuesday with NW flow aloft
becoming more zonal by Wednesday. This will allow an abundance of
Pacific moisture to move across the northern Rockies and into the
northern tier as sfc low pressure develops lee of the Rockies and
moves across the plains. Models continue to show a band of snow
across the CWA Wed aftn...for the best chance of widespread snowfall
accumulations in the long term period. Models are showing
significant snowfall accumulation in the Cascades/Northern Rockies
so QPF amounts still in question as well as track of sfc features,
but do think one to three inch accumulations across at least eastern
ND is possible. QPF amounts and calculated snow fall accumulations
did come in a bit lower today which makes sense with what is
expected in the PAC NW. Beyond Wed, low chances of snow continuing
across the far south into Friday but main feature is a push of cold
air that brings Christmas Eve highs possibly into the single digits
below zero across the northern two thirds of the CWA. Adjusted
temps with a 50/50 Superblend/CONSALL solution for Thu-Sun, however
coldest temps will be dependent on cloud cover, winds, and where
exactly the freshest snowfall sets up mid week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 629 PM CST Sun Dec 17 2017
LIFR conditions at TVF trying to work into FAR and BJI this
evening as low stratus deck with fog lifts to the north and
expands in coverage this evening across NW MN. Stratus deck will
persist into the overnight before it slides to the east towards
morning.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...JK
SHORT TERM...TG
LONG TERM...Speicher
AVIATION...JK
Area Forecast Discussion
National Weather Service Grand Rapids MI
942 PM EST Sun Dec 17 2017
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 323 PM EST Sun Dec 17 2017
Milder weather can be expected much of this week, especially
compared to the last couple of weeks. there is a chance of some
precipitation tonight as a frontal system approaches the area.
Significant precipitation is not expected, although types could range
from rain, to snow, to some freezing drizzle depending on
temperatures.
The precipitation will clear out by Monday night, and some sunshine
and temperatures well into the 40s can be expected.
The end of the week will see chances for precipitation increase as a
major storm system affects much of the country. This system could
bring rain or snow to the area. Behind the system for the upcoming
Christmas holiday, colder weather is expected to settle back in with
chances for lake effect.
&&
.UPDATE...
Issued at 942 PM EST Sun Dec 17 2017
I updated the chance of precipitation to likely over most of our
forecast area overnight. As the day shift forecaster wrote, we
will have P-type issues as surface temperatures at this hour are
still mostly below freezing. Model sounding suggest areas near and
south of I-96 will be warm enough for mostly rain but if the air
temperature does not get above freezing before the precipitation
begins we may see some freezing rain or freezing drizzle. Also as
noted by the day shift forecaster, the DGZ will for the most part
not be saturated during the precipitation event expect for a short
period north of I-96 in the pre-dawn hours. So, while I do now
think most areas will see a between 0.01 and 0.05 inches of
precipitation between 3 am and 10 am temperatures will be near to
above freezing. Typically to get a significant amount of ice air
temperatures need to be below 30 degree, below 28 degrees is even
better. I do not think anyplace in our CWA will be that cold when
liquid precipitation is falling. So I do not believe we need a
Weather Advisory for this event.
So, why is it going to precipitate early Monday morning? Turns out
we have the right entrance region of a northern stream jet core
over upper Michigan tonight while a much stronger southern stream
jet core passes over I-80 (130kts). There is a PV wave that is
associate with an northern stream trough (seen on water vapor
loops) heading this way assoicated with all of this. This results
in area of enhanced 1000/850 mb moisture transport aimed at I-94
to I-96 between midnight and sunrise. Also there is 30 to 40 knot
low level jet associate with the jet entrance region that moves
into Southwest Michigan toward sunrise. All of this working
together results in enough lift for some light precipitation.
It should all be done with by late morning.
There is an issue with fog but with all the clouds an
precipitation it would seem to me that will not be a big issue
overnight.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 323 PM EST Sun Dec 17 2017
Our main issues in the short term are pcpn trends and type for
tonight and into Monday. The good thing is that impacts will be
limited to a chance of some light freezing drizzle tonight and Mon
morning where temps will be below freezing.
Pcpn has tried to make it up north into the area this afternoon, but
has not, and will likely not succeed as the deep moisture and wave
gets shunted away from the area. We will see better moisture advect
in later tonight from the SW, and interact with a weak front coming
in from the NW. This will help to develop some pcpn over the heart
of the area.
Pcpn will be light in nature. P-type issues are present as the
atmosphere is initially supportive of snow. The warmer air coming in
will try to change pcpn over to some light rain. The sfc temps will
drop off a couple of degrees this evening, before coming up
gradually overnight.
On either side of the best chance of pcpn (roughly from after
midnight to daybreak) the DGZ will not be saturated. This will lead
to some drizzle/freezing drizzle potential depending on the sfc
temp. This should be light and limited in time due to rising temps.
We do not think it will be significant enough for any headlines at
this time. Fog will become possible also overnight with saturated
lower levels.
Some light pcpn will linger into the first half of Mon before the
front clears out the moisture later in the day.
The remainder of the period from Mon night through Tue night looks
fairly quiet. There will be a system well north of the area that
could bring some flurries into the U.S.-10 corridor on the srn
flank. That will move out, and eventually we will see clearing take
place for Tue. Temps on Tue with sunshine and nice warm air
advection will likely climb well into the 40s.
.LONG TERM...(Wednesday through Sunday)
Issued at 323 PM EST Sun Dec 17 2017
The main challenge in the long term deals with the impacts from the
storm for the end of the week.
Models are in reasonable agreement in showing warm air advection
will be underway Wednesday night into Thursday. The combination of
lift and deepening moisture will result in some snow. Overall the
impact potential looks limited as the low levels remain relatively
dry. There are some indications that a warm above freezing layer
will try to move in aloft on Thursday. If this happens we could see
more potential for liquid precipitation.
The GFS suggests a deeper further west track to the storm...bringing
the warm sector into Southwest Lower MI on Friday. While the High
Res Euro tracks the low through the central parts of the CWA and
keeps the storm weak. Either way any mixed precipitation Thursday
night should change over to all rain. There is some risk for a
slick Friday morning commute...that will need to be monitored. I
would not rule out some freezing rain as well.
If the GFS is right...there could be thunderstorms around Friday.
Elevated instability is seen in the model with some suggestion of
surfaced based instability as well. The High Res Euro shows much
less potential for that to happen. Will not introduce storms at
this point...but will need to monitor trends closely in the coming
days.
As the colder air starts to work in behind the departing
storm...will feature falling temperatures. At this point the
potential for impactful lake effect looks low for Saturday into
Sunday. There are indications that a wave may form along the
frontal zone on Sunday which could lead to an increased risk for
snow.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 625 PM EST Sun Dec 17 2017
While it is hard to tell from IR satellite loops skies have
cleared below 12,000 ft at AZO, BTL, JXN and BIV and should soon
do the same at GRR. Maybe even MKG and LAN will clear of the low
clouds for a few hours this evening. This is shown well by the
HRRR Layered cloud forecast, which by the way is tracking nicely
over the past 3 hours. So, I used the HRRR Layered cloud forecast
to do the 00z TAFS.
The low clouds will fill back in by 06z or so at all TAF sites.
There is a wave on the front that comes through the area toward
morning. This should bring some light rain or drizzle to our TAF
sites. The glitch is temperatures are currently below freezing at
MKG and GRR and near freezing at LAN. The other TAF sites are 33
degrees. It would not be out of the question this could be
freezing rain. However the hi-res models show winds becoming more
southerly than easterly overnight. That will bring up the warmer
air from the south into our area mitigating the risk of freezing
precipitation. Still it is not out of the question. That should
more out of the area prior to noon, then just low clouds and some
light fog the rest of the day Monday.
&&
.MARINE...
Issued at 323 PM EST Sun Dec 17 2017
We will be issuing a Small Craft Advisory that will be effective Mon
afternoon through Tue. This will likely need to be extended out in
time eventually, but we do not want to go too long for the time
being. Winds pick up after the front/wave move through tonight into
Mon morning. A decent gradient sets up, and will likely last into
Tue night before diminishing enough. Waves will build up to around 8
feet or so.
&&
.HYDROLOGY...
Issued at 323 PM EST Sun Dec 17 2017
A few gauge sites remain ice affected, most notably the Looking
Glass at Eagle and the White River at Whitehall. Of the two, Eagle
is the only site with a level confirmed to be above bankfull.
All sites are stable at this point and the Looking Glass River
continues to recede. Improvement is expected to continue with warmer
temperatures over the course of the work week. Precipitation is also
manageable with only a few tenths of an inch forecast through the
next 7 days.
Flood risks are minimal. For now, concerns are largely focused on
behavior existing ice jams. Otherwise, no addition flooding is
expected at this time.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from 2 PM Monday to 7 PM EST Tuesday for
LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MJS
AVIATION...WDM
HYDROLOGY...JAM
MARINE...NJJ
Area Forecast Discussion
National Weather Service Lincoln IL
823 PM CST Sun Dec 17 2017
.UPDATE...
Issued at 823 PM CST Sun Dec 17 2017
Some scattered areas of light rain continue across the northern
third of Illinois this evening, with short range high-res models
suggesting will continue through the night. Further south, it
should be more of a patchy drizzle, though this will wait until we
start getting a more widespread low stratus overhead. Latest
observations showing a large part of the forecast area southeast
of the Illinois River and north of I-70 with clouds as high as
about 5,000 feet, though this will lower the rest of the evening.
Temperatures should hold fairly steady or only fall a couple
degrees at best. Updated zones/grids have been sent for the latest
trends.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 310 PM CST Sun Dec 17 2017
Mid afternoon surface analysis shows weak 1015 mb low pressure
over south central Iowa with its warm front extending eastward
across northern IL, just north of I-88. A few light rain showers
lingered north of Lincoln and the latest HRRR models continues
isolated light rain showers over northern CWA into this evening.
Several large breaks in the clouds over central and eastern IL has
allowed temps to elevate into the mid 40s to lower 50s, coolest in
southeast IL. Low/stratus clouds over MO along with some fog and
drizzle will spread ne across central IL during this evening and
linger into Monday morning. Lows tonight only in the upper 30s to
around 40F as sw winds 5-10 mph continue.
Low clouds to decrease from the west during Monday afternoon
though eastern IL likely stays mostly cloudy much of the
afternoon. SW winds 8-15 mph to keep temps on the mild side with
highs 50-55F, while areas ne of I-74 in the upper 40s.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 310 PM CST Sun Dec 17 2017
Skies to become mostly clear during Monday night with sw winds
prevailing, and lows only 35-40F. Tue still looks like a nice day
with partly to mostly sunny skies and highs in the low to mid
50s, even upper 50s sw CWA. A weak cold front pushes through
during Tue afternoon and should come through dry with winds
shifting nw behind it. Models track a low pressure over southern
AR and the southern TN river valley during Tue night keeping its
precipitation south of our CWA, though southern areas will see
more cloud cover. Lows Tue night in the upper 20s northern CWA
and mid 30s along highway 50 in southeast IL. Low pressure tracks
toward the Carolina coast by sunset Wed while weak upper level
ridging into IL keeping us dry. Cooler highs Wed in the 40s with
E/NE winds of 5-10 mph. These temps are still about 10F above
normal.
Models deepen a strong upper level trof over the Rockies Wed night
and Thu and continue trending slower ejecting low pressure into
central KS by early Thu afternoon and near the IA/MO border later
Thu evening. Thu now looks dry across CWA even nw of the IL river
valley with just a slight chance of light rain later Thu evening.
Another seasonably mild day Thu in the upper 40s and lower 50s,
with some mid 50s southern CWA. Have slight chance of mainly light
rain showers overnight Thu night across CWA with a mix possible nw
of IL river later Thu night. Lows Thu night range from mid 30s
over IL river valley, to lower 40s in southeast IL from I-70 se.
Surface low deepens into the western Great Lakes by Fri evening
while another low pressure moves into the southern TN river valley
by overnight Fri night. This will likely develop precipitation
across central and eastern IL during Friday and then diminish from
the west during overnight Fri night. Should be warm enough for all
rain on Friday, then changing to a mix or snow from nw to se
during Fri evening and over southeast IL early overnight Fri night.
Could be some light snow accumulations Fri night up to about 1
inch. Highs Fri range from lower 40s nw of IL river to mid 50s by
Lawrenceville. Drier and colder air ushers in on Sat on nw winds.
Lows Fri night in the low to mid 20s in central IL and upper 20s
to around 30F in southeast IL. Highs Sat and Sunday in the upper
20s and lower 30s over IL river valley and upper 30s to near 40F
in southeast IL. Extended models have different solutions for
next Sunday with active southern stream se of central IL and also
a northern stream system moving into the Midwest. Stayed close to
consensus for pops next Sunday which has 20-30% chance of snow
over the IL river valley. But chances of snow could increase
further east across area on Christmas eve/Sunday and Sunday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 522 PM CST Sun Dec 17 2017
Currently watching an area of MVFR/IFR ceilings advecting
northeast out of Missouri and southern Illinois. Ceilings over
the central Illinois TAF sites are around 5-7kft as of 23Z, but
will be steadily lowering over the next few hours. Some IFR
conditions expected by about 05Z or so, along with some patchy
drizzle. While ceilings should start to lift Monday morning, it
likely will take until afternoon before rising above 3,000 feet.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SHORT TERM...07
LONG TERM...07
AVIATION...Geelhart
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
851 PM EST Sun Dec 17 2017
.UPDATE...
Issued at 815 PM EST SUN DEC 17 2017
Hourly pops, sky, temperatures and dewpoints have been updated
based on recent observations. Clouds heights are still expected to
decrease overnight with subsidence in the wake of the mid level
wave that brought precipitation earlier today. Stratus build down
to the ridgetop level if not lower should occur overnight. This
and weak southwest flow from about 900 mb and below and a weak
passing disturbance could still lead to some drizzle. Recent radar
images generally just have what appears to be patchy drizzle
across the 4 VA border counties and adjacent areas of far southern
portions of counties just to the north. Overall, other than some
adjustments for recent observation and radar trends, no
substantial changes were made at this point.
Although drizzle later on tonight is low confidence, confidence in
the persistent low clouds and rather mild temperatures is high.
Min T will be in the upper 30s and little drop in temperatures
overnight from current readings.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 345 PM EST SUN DEC 17 2017
20z sfc analysis shows low pressure working into Kentucky with a
weakening cold front spreading into our area. This is continuing
to support light pcpn and a lowering cloud deck late this
afternoon. Under the thick clouds temperatures are holding in the
upper 30s to lower 40s most places while dewpoints are in the low
to mid 30s. Winds are predominantly light and variable with the
higher elevations and locations closer to the Bluegrass seeing
southwest ones. They are light to the northwest with stronger ones
at 10 to 20 kts above 2000 feet along with some gusts in the 30s.
The models are in good agreement aloft through the majority of
the short term portion of the forecast, though they diverge a bit
late. They all depict fast and nearly zonal flow over the Ohio
Valley tonight through Monday night. A dampening wave is currently
departing the area with additional energy more concentrated well
to the north of Kentucky on Monday. Meanwhile, a fairly deep and
closed trough will be swinging through the Four Corners region
tomorrow afternoon elongating as it heads into western Texas by
Tuesday morning. At this point the models start to stray from each
other with the NAM taking the core of the trough further north
than the GFS and ECMWF. This difference continues through the day,
Tuesday as the ECMWF digs its trough deepest and a bit quicker
east than the others. Downstream, this will affect the amount of
height rises over Kentucky with additional bits of energy slipping
over the JKL CWA. Given the increasing model spread a general
blend is preferred, though the higher resolution HRRR and NAM12
were leaned upon for wx details.
Sensible weather will feature plenty of clouds through the short
term as low level moisture will be tough to clear out. With
lowering cigs tonight into Monday drizzle and pockets of light
rain can be expected but very little in the way of QPF resulting.
In addition the cloud cover will really tamp down the diurnal
curve through the entire short term period of the forecast. With
the falling cigs some may get low enough tonight for areas of
ridgetop fog. Have included this in the grids, as well.
Given the limited diurnal range did not deviate too far from the
ShortBlend temperatures through the period. Did raise PoPs a notch
during most of the short term to help define the drizzle threat.
.LONG TERM...(Tuesday through Sunday)
Issued at 250 PM EST SUN DEC 17 2017
The latest model data is suggesting that there will be two periods
of active weather in the extended. The first will be from Tuesday
afternoon through Wednesday evening, as an area of low pressure
moves slowly across the Tennessee Valley. Scattered to numerous rain
showers are expected for most of the area, as the weather system
makes its way off to the east. The second period of active weather
looks to be from Friday through early Saturday evening. It appears
once again that temperatures will be warm enough to keep any
precipitation in liquid form across the area. Both precipitation
episodes should provide nothing more than a good soaking rain to
eastern Kentucky.
Temperatures through out the period are expected to be well above
normal, with daily readings topping out in the 50s for most
locations. There will be a few days where some spots will only make
into the upper 40s, and other days where highs will be in the upper
50s. Nightly lows are forecast fall into the 30s and 40s, which
would also be well above normal for this time of year.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 735 PM EST SUN DEC 17 2017
After this, lingering low level moisture behind the system that
brought precipitation from late Sunday morning into Sunday
evening will remain in place through the period. Generally MVFR
CIGS and or VIS are reported areawide. VIS is lowest on average
in the north and along the highest peaks near the VA border. Weak
south to southwesterly flow generally at or below 925 mb tonight
should lead to further saturation from the ridges above 2000 feet
MSL to the ridgetops further north and west. This and a weak
disturbance should also lead to the potential for drizzle and CIGS
lowering through the MVFR range and to IFR CIGS for ridgetop
airports of KSYM, KSJS, and KJKL as well as LOZ during the 6Z to
15Z period. Ridgetop vis should also decrease during that time
with stratus build down fog and it may be dense in some
instances. Some improvements into the MVFR range is possible by
the last 6 hours of the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...JP
Area Forecast Discussion
National Weather Service Louisville KY
732 PM EST Sun Dec 17 2017
.Forecast Update...
Issued at 732 PM EST Sun Dec 17 2017
Patchy drizzle is already occurring across the area so did a quick
update to get drizzle in the grids a little earlier than originally
planned. No other changes.
&&
.Short Term...(This evening through Monday night)
Issued at 230 PM EST Sun Dec 17 2017
As of mid afternoon, regional radar imagery showed an area of
showers generally along and east of the I-65 corridor across the
lower Ohio Valley. Readings were in the low to mid 40s with overcast
skies.
The main forecast concern in the short term is drizzle and fog late
tonight through Monday and its impact on temperatures. For the
remainder of this afternoon, plan on the back edge of the
precipitation to quickly move east, giving way to just cloudy skies
by late afternoon. As we head into this evening, the low levels of
the atmosphere will begin to moisten and saturate from the surface
to about 850 mb. Upstream observations show plenty of 500 to 1000 ft
ceilings with 3-5 mile visibilities. RAP and HRRR soundings show
good signals for drizzle beginning toward midnight. Tonight`s
temperatures won`t drop too much with the widespread cloud cover.
Plan on lows in the low 40s.
Drizzle, fog, and low clouds will start the new work week. We should
stay socked in the stratus for most of the day as well. This should
keep our highs held down to the low to mid 50s. Some breaks in the
clouds are possible late in the day and into Monday night but
overall not optimistic that we`ll see much clearing. Lows Monday
night will stay in the low to mid 40s.
&&
.Long Term...(Tuesday through Sunday)
Issued at 235 PM EST Sun Dec 17 2017
Several weather systems to keep tabs on in the long term period, the
first being Wednesday. Confidence in the overall forecast starts
above average early on then drops considerably by next weekend and
Christmas.
An upper level system coming from the southwest US will lift toward
the Tennessee Valley by late Tuesday into Wednesday. Rain showers
are likely to spread into Tennessee and southern Kentucky late
Tuesday then across more parts of central Kentucky Wednesday
morning. The trend in the model cycles has been to the north, and
the latest model consensus brings in precipitation chances up to the
Louisville metro now. However, the highest chances (greater than 50
percent) remain confined closer to the Tennessee border. There`s
good agreement that the rain will exit Wednesday afternoon or
evening. Plan on highs to be in the upper 40s to middle 50s. Right
now, up to 1/2 inch of rain could be possible along the KY/TN
border.
A deep upper level trough is then forecast to develop across the
central US. This will act to bring ridging across the southeast US
and warmer temperatures. Thursday`s highs could reach the upper 50s
to near 60, with lower 60s possible across southern Kentucky.
A strong cold front is then forecast to approach the area late
Friday into early Saturday. The 17.12z models generally have the
frontal passage late Friday. Showers will become likely ahead of the
front during the afternoon or evening hours then a more widespread
band of showers will accompany the frontal passage. Soundings show
the potential for marginal MUCAPE (100-500 J/kg) developing so
couldn`t rule out a few thunderstorms at this time. By early
Saturday morning, crashing temperatures behind the front could
briefly turn any remaining precipitation over to a mix or wet snow
west of I-65.
For Christmas Eve and Christmas Day, the forecast confidence drops
off. This cycle of models continue to struggle with the strength of
a building southeast US ridge. The ECMWF and CMC kept a stronger
ridge with a more active, but warmer, zone of weather from the Texas
Gulf Coast through the lower Ohio Valley into the Great Lakes. The
GFS was a colder, but drier solution. It remains too early to
pinpoint details and the best message we have is to continue to
closely monitor the forecast this upcoming week for any holiday
travel preparations.
&&
.Aviation...(00Z TAF Issuance)
Issued at 629 PM EST Sun Dec 17 2017
Sfc-850 RH will remain high through much of the TAF period.
Ceilings, already MVFR at the start of the TAF at most locations,
will lower tonight to IFR, possibly with some LIFR during the early
morning hours especially at BWG and LEX. The low level moisture will
remain in place on Monday so low clouds will persist through the
day, though there should be enough mixing to push ceilings back up
into MVFR.
Winds will come in from the southwest at 5 to 10 knots with surface
ridging to our east and southeast and a cold front approaching from
the northwest by the end of the period.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...13
Short Term...ZT
Long Term...ZT
Aviation...13
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
830 PM EST Sun Dec 17 2017
.SYNOPSIS...
A weak boundary overhead will lift to the north as a warm front
tonight into Monday. An upper level disturbance will approach
the area from the west Monday afternoon and evening. This
disturbance could bring some light precipitation to the
Appalachian Front later Monday. High pressure will build in
briefly before the next storm system scoots by to our south
during the middle of the week.
&&
.NEAR TERM /THROUGH MONDAY/...
A warm front was stationed just north of the Potomac River as
of 8 PM. Removed mention of sleet along the Mason-Dixon line as
dew points have risen to 30+ degrees and air temperatures are
in the lower 40s. Wet bulb 0 C heights are, at best, 2500 feet.
Otherwise, forecast on track with sprinkles or spotty light
rain ending this evening as the warm front lifts north. Skies
are expected to remain mostly cloudy overnight. Low temperatures
will bottom out near or slightly above freezing outside of the
major cities, upper 30s in the downtown areas.
As for the upslope areas west of the Allegheny Front,
moisture/lift appear too shallow/weak for appreciable snowfall
accumulation. Some light rain and drizzle mixed with pellets or
snow grains seems most likely, with perhaps a light coating at
the highest elevations between midnight and daybreak before
temperatures warm.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As a warm front pushes to the north Monday, so do the milder
temperatures will highs about 5 degrees warmer than Sunday. A
light persistent southwest wind will aid in this milder trend.
By Monday afternoon into Monday evening, clouds and precipitation
will return with the bulk of any precipitation remaining light
and mainly confined to the Appalachian Front in the form of
light rain or drizzle. A leeside trough of low pressure should
set up just to the east of the Appalachian spine, thus, allowing
for this precipitation to occur with the help from a weak mid-
level disturbance.
Tuesday should be even milder yet with highs ranging from the
middle 50s to the middle 60s widespread across the region. A
persistent southwest wind and a little added sunshine during the
day should aid in this. Tuesday night will be about the same as
Monday night with low temperatures dropping into the middle to
upper 30s for the most part.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Southern stream shortwave energy will be approaching the Mid-Atlantic
region on Wednesday into Wednesday night. Guidance suggests that the
forcing will stay south of us, but showers associated to this system
could reach the southern counties of our CWA. Still to be determined
in more detail is timing and p-types.
A ridge of high pressure builds over the region on Thursday and into
Thursday night bringing a period of dry weather. Sometime on Friday
a warm front will push through, followed by a cold front on Saturday.
Models suggest that Friday will remain on the drier side while Friday
night we might see showers ahead of the front, but it all depends
on the timing of it. Saturday`s PoPs are higher with the front moving
through the region from the west. Uncertainty exists on Sunday`s
weather depending on how close to the area the front stalls.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Winds generally southwest less than 5 knots through Monday. VFR
conditions expected tonight through Tuesday night. HRRR hinting
at some MVFR visibility 9-12Z INVOF IAD/BWI/MTN tonight. Can`t
rule out brief patchy fog in these areas if breaks in clouds
develop given high RH values/calm winds.
Some guidance (namely the MET) is hinting at fog development
near the Bay Monday night which makes sense given light winds
and environmental dew points higher than water temperatures.
Mainly VFR conditions expected the second half of the week.
&&
.MARINE...
No marine hazards through Monday night. Winds become light and
variable tonight, then southwest 5-10 kts Monday into Tuesday.
Fog is possible over the waters Monday night which makes sense
given light winds and environmental dew points (mid to upper
40s) higher than water temperatures (around 40).
Winds should increase late Tuesday into Wednesday near and behind
a cold front. Small Craft Advisories may be needed for portions
of the waters during this time. Near shore waters likely see
gusts first since open waters will be much cooler than
environmental airmass. Mixing would presumably be more
difficult over open waters until a cooler airmass arrives later
Tuesday night into Wednesday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...KLW
NEAR TERM...KLW/DHOF
SHORT TERM...KLW
LONG TERM...IMR
AVIATION...IMR/KLW/DHOF
MARINE...IMR/KLW/DHOF
Area Forecast Discussion
National Weather Service Midland/Odessa TX
518 PM CST Sun Dec 17 2017
.DISCUSSION...
The latest Aviation Discussion is included below.
&&
.AVIATION...
VFR conditions will prevail most of the night at all area
terminals. However, fog may form late, if not an IFR ceiling, and
have included these lower conditions at all but KCNM and KFST.
Since there is some uncertainty on timing and extent, have only
put temporary IFR ceilings and MVFR visibility at the rest of the
terminals. If an extensive low cloud deck forms, sites may be
affect through 18/17Z.
&&
.PREV DISCUSSION... /issued 226 PM CST Sun Dec 17 2017/
As of 2:00 PM CST Sunday...For the Christmas weekend the only
thing consistent is the inconsistency of the medium range models.
At least for this 12Z suite of models the GFS...ECMWF...and
Canadian are not consistent with themselves let alone with each
other. We`ll see where this game of musical models stops over the
next several days.
In the short-term the HRRR and RAP13 are indc ample low level
moisture moving into portions of the area.Therefore have put in
patchy fog (temps should remain above freezing so no freezing fog
is expected) for the central and eastern portions of the CWA late
tonight into Monday morning. The upper low over extreme southwest
Arizona will weaken as it lifts northeast into the TX Panhandle
on Tuesday. Have pulled back pops and have just kept them in for
the extreme western portions of the CWA...temps will be warm
enough for all rain. Have kept pops in the southeast CWA on
Tuesday with the deeper moisture.
In general...all the medium range models keep the CWA dry with
above normal temps thru Thursday (normal for MAF is 57). As
mentioned above the models are not consistent for the holiday
weekend...with the GFS and ECMWF now significantly warmer and the
Canadian much colder. Due to this inconsistency have not made any
changes to the extended forecast...since we want to avoid making
big changes (at least to we see some consistency).
Strobin
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 38 59 43 62 / 0 10 10 10
Carlsbad 38 60 40 62 / 10 10 10 0
Dryden 42 64 47 69 / 0 0 20 10
Fort Stockton 40 63 44 64 / 0 0 10 10
Guadalupe Pass 41 53 37 52 / 20 10 10 0
Hobbs 36 58 38 60 / 0 0 10 10
Marfa 35 62 36 58 / 0 0 10 10
Midland Intl Airport 38 60 40 62 / 0 10 10 10
Odessa 38 60 40 62 / 0 0 10 10
Wink 38 60 40 63 / 0 0 10 10
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
49/33
Area Forecast Discussion
National Weather Service Marquette MI
535 PM EST Sun Dec 17 2017
.SHORT TERM...(This evening through Monday)
Issued at 356 PM EST SUN DEC 17 2017
WV imagery and RAP analysis indicated mainly zonal flow through the
nrn CONUS and srn Canada with a shortwave trough over nrn Ontario
near CYPL. At the surface, weak srly flow prevailed as high pres
moves to nrn New England and low pressure develops over the plains.
Radars indicated weak returns from nw Wi into Upper Michigan with
sfc reports showing some light snow over far nrn WI.
Tonight, expect the light snow, supported by 800-600 fgen to slide
through the cntrl and ern cwa this evening. However, with only weak
to moderate forcing and little moisture inflow, only lower end POPs
were included with little or no accumulation expected. Any lingering
light snow should end by around 06z.
Monday, southwest winds will increase as a deep low moves through
cntrl Canada to far nw Ontario. WAA will help push temps above
seasonal averages with highs in the lower to mid 30s. A shortwave
moving toward nrn MN, with upper level div in the left exit of the
250-300 jet, may help to spread some light snow into wrn Lake
Superior and possibly into the far wrn cwa late.
.LONG TERM...(Monday night through Sunday)
Issued at 347 PM EST SUN DEC 17 2017
Monday night through Wednesday: A series of embedded trough axes
rounding a broad mid-level low over Hudson Bay will brush the CWA
the during this time. A strong surface pressure gradient juxtapose
with a favorable isallobaric wind will promote gusty W/WNW winds
late Monday night into Tuesday evening. 925-850hPA winds of 40-45kts
should allow for surface gusts to 40mph across the Keweenaw
Peninsula late Monday night through much of Tuesday. Though 850hPa
temps of just -10 to -12C and reduced residence time from the
stronger winds will limit LES intensity, intermittent white out
conditions will be possible given the added component of blowing
snow from the current snowpack. This concern will also translate to
the immediate shore of Lake Superior from Munising eastward Tuesday
evening.
As noted, LES should be limited early on Tuesday, but a secondary
trough axis will bring more favorable thermodynamic conditions for
LES Tuesday evening. A period of moderate LES will be possible for
the W to NW wind snow belts Tuesday night into Wednesday before
lowering inversion heights subdue the LES into Wednesday evening.
Wednesday night through Sunday: As can be expected this time of
year, model guidance continues to show decent run-to-run differences
with the evolution of the large scale pattern and associated period
of active weather across the western Great Lakes. The main message
is that high-impact weather may affect early holiday travel
somewhere across the region during this time.
Light WAA snow should spread across the CWA late Wednesday evening
into Thursday morning, producing sub-advisory accumulations across
the SW half of Upper Michigan. Guidance begins to diverge after this
as notable disagreement develops with the handling of lee
cyclogenesis in the central and southern Plains as a mid-level
trough ejects from the four corners region. Contrary to yesterday,
the GFS has become the strongest and northern most solution with
this low, bringing a period of high-impact snowfall to Upper MI late
Thursday morning into Friday night. The ECMWF and CMC model bring a
broader swath of moderate snow across Upper MI Thursday evening into
Friday, keeping more significant precipitation well south of the
region. Again, given the highly varying solutions, providing any
detailed forecast is nearly impossible at this point. However, those
who could be affected by moderate to heavy snow accumulations in the
western Great Lakes Wednesday night into Saturday should continue to
monitor forecast updates through the upcoming week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 535 PM EST SUN DEC 17 2017
There is enough low level moisture upstream that conditions will
continue to be in the IFR/LIFR range for the most part tonight. More
substantial dry advection with improving conditions is expected
Monday afternoon with improving conditions.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST SUN DEC 17 2017
Southwesterly winds will increase to 20 to 30 knots Monday over the
west and north central portions of Lake Superior possibly reaching
gales late Mon afternoon and evening before veering to northwesterly
gales to 35-40 knots late Mon night into Tue night. With increasing
wave heights and colder air temperatures, freezing spray is possible
Tuesday night into Wednesday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Watch from late Monday night through late Tuesday night for
LSZ243>245-264>267.
Gale Watch from Tuesday morning through Tuesday evening for
LSZ162-241-242-246-247-263.
Gale Watch from Tuesday morning through late Tuesday night for
LSZ248>251.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...Kluber
AVIATION...07
MARINE...JLB
Area Forecast Discussion
National Weather Service Norman OK
859 PM CST Sun Dec 17 2017
...Update...
&&
.DISCUSSION...
Based on trends we have issued a Dense Fog Advisory for portions
of central and southern Oklahoma.
Despite cirrus, we can faintly see back edge of low stratus
working northeast across south-central Oklahoma in IR shortwave
imagery. As this occurs, radiative cooling will increase enough
for fog formation given how moist the low levels remain. Cirrus
may temper radiative cooling some, but not enough to prevent
several locations from falling to around or possibly below one
quarter mile later tonight.
Further east where low stratus remains, low level saturation has
been deep enough for persistent light drizzle in/around Shawnee
and Chandler to near Ada. This should gradually diminish as depth
of saturation decreases per RAP and HRRR forecast soundings. Once
this happens, and especially when/if low clouds clear, dense fog
may occur across these areas and we will probably need to expand
the advisory eastward.
Across southwest Oklahoma, light winds and at least modest
radiative cooling beneath cirrus will probably eventually result
in fog, but we kept the advisory out of these counties for now
given the fairly large T/Td spread. We may need to expand west to
include a few more counties later tonight.
Otherwise the forecast remains on track. Earlier we lowered
temperatures considerably across the northwest where cirrus is
not present and good radiative cooling is expected.
Minor/insignificant adjustments were made elsewhere to various
weather elements.
BRB
&&
.PREV DISCUSSION... /issued 517 PM CST Sun Dec 17 2017/
AVIATION...
Area of low clouds will gradualy clear across western sites, but
expect that after sunset that this dissipation of the clouds will
slow or stop through much of the night. Therefore will keep a MVFR
ceiling at OKC/OUN/PNC through the night with some patchy fog
late. Will also mention the possibility of some fog at most sites
overnight, but with lack of moisture west and cloud cover east,
will keep visibility at 1 mile or higher. Will have to monitor
closely however. Expect VFR conditions to overspread the area by
mid-morning with some afternoon high clouds streaming in from the
southwest. Winds will remain light.
PREV DISCUSSION... /issued 355 PM CST Sun Dec 17 2017/
DISCUSSION...
For tonight, fog will be the primary issue. Dew points are
currently in the low to mid-40Fs across the eastern two-thirds of
Oklahoma and adjacent parts of north Texas. As skies clear from
the west, temperatures are expected to cool info the mid-30Fs to
40Fs in this area. With a such a large difference in dew points
and forecast low temperatures, fog (potentially dense) is expected
to develop later tonight across the eastern two-thirds of the area.
By Tuesday, a closed-low is forecast to lift northeastward
into the Southern Plains. Rain is likely across southeast Oklahoma
as this system passes by the area. Some thunder is still possible
as well with some elevated instability. Rain chances decrease
with north and west extent. Dry and above-average temperatures
are expected in the system`s wake for Wednesday.
For the frontal timing on Thursday, both the 17/12Z GFS and
ECMWF have slowed the cold front down due to a slower passage of
the attendant shortwave trough. Therefore, another warm day is
expected for Thursday with the cold front entering northwest
Oklahoma late afternoon. The slower timing may allow greater
moisture advection ahead of the front, which may result in a
better chance of rain across eastern Oklahoma Thursday night.
The air mass behind the initial cold front may not be as cold as
previously forecast with the primary longwave trough remaining to
the west as the initial shortwave lifts northeastward. Therefore,
forecast high temperatures are slightly warmer for Friday and
Saturday afternoons.
By Sunday, there continues to be disagreement between the GFS and
ECMWF. The previous runs of each model don`t even agree with each
other. Even within the GEFS (GFS Ensemble Forecast System), there
is high variance among the 20 members--so overall predictability
continues to be very low in this period.
At this time, the ECMWF and Canadian models are in closest
agreement with a high-amplitude ridge off the east coast and a
high-amplitude trough across the western United States. This
places the Southern Plains within a baroclinic zone/faster flow
aloft. A secondary surge of colder air may advect southward on
Sunday as well. Will maintain a low chance of snow for Sunday,
primarily across northwest Oklahoma, as embedded waves within the
southwest flow could result in snow.
With the continued uncertainty, the bottom line is exactly the
same as yesterday: Colder weather is expected late this week with
at least a low chance of winter precipitation next weekend--but
specifics are yet to be determined.
There are some indications that even colder weather will be
possible beyond this forecast period as another surge of cold air
moves southward.
Mahale
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 47 38 59 45 / 10 0 0 10
Hobart OK 49 35 55 41 / 0 0 10 10
Wichita Falls TX 54 38 56 47 / 0 0 10 10
Gage OK 48 25 60 37 / 0 0 0 0
Ponca City OK 49 38 56 41 / 10 0 0 0
Durant OK 50 43 56 50 / 10 10 10 20
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Dense Fog Advisory until 9 AM CST Monday for OKZ018-019-023>031-
038>042-045>047-050-051.
TX...None.
&&
$$
12/30
Area Forecast Discussion
National Weather Service Tucson AZ
135 PM MST Sun Dec 17 2017
.SYNOPSIS...Valley rain and mountain snow showers associated with
slow moving low pressure south of Arizona will gradually dissipate
tonight as the low moves east. Wraparound moisture will allow for
some lingering mountain snow showers east of Tucson on Monday, but
drier air will move into the area through mid week. A trough will
sweep through the Four Corners late in the week bringing increased
cloud cover and cooler temperatures, but at this time it doesn`t
look to bring much in the way of precipitation. Cooler temperatures
will linger through next weekend.
&&
.DISCUSSION...
Scattered rain and snow showers continue across the area this
afternoon, although areal coverage is substantially less than what
was seen earlier this morning. Upper low has moved little today
although water vapor imagery clearly shows that a lobe of shortwave
energy has already moved through southeast Arizona and is pushing
eastward into New Mexico. Regional radar imagery is showing another
round of precip forming south of Tucson as of 20Z and this fits well
with the past few runs of the HRRR. After 00Z the HRRR isn`t very
enthused with precip chances for the rest of the night, only
depicting widely scattered showers across the area. I`ll leave the
Winter Wx Advisory in place as is to account for the precip that`s
about to move through the area as it`ll easily produce a few inches
of snow above 6000ft. If things quiet down after sunset the Advisory
can always be cancelled a few hours early.
Precip chances don`t go away completely as the upper low and its
associated moisture will slowly shift into New Mexico on Monday.
Wraparound moisture could result in scattered valley rain/mountain
snow showers along the AZ/NM border tomorrow although any snow
accumulations would be light and it doesn`t appear they`d be enough
to warrant the extension of the aforementioned Advisory. The low
will finally exit the area Monday night with drier air moving into
the area. Dry weather with below normal temps will prevail through
mid week.
The potential for a mid/late week storm still exists, but today`s
deterministic 12Z runs keep the storm track well north of the area
and only depict an increase in clouds and wind coincident with the
passage of the trough. GEFS plumes aren`t enthused about precip
chances either, same story with the EC ensemble mean QPF (a few
hundredths of an inch in the White Mtns, that`s about it). Very low
(single digit) precip chances later this week look to be all that
are warranted at this point. The trough will usher in much cooler
air to the area with widespread freezing or near freezing temps
possible to close out the week into the weekend. If the current
forecast verifies we may need to look at freeze warnings for the
deserts before all is said and done.
Looking forward to Saturday/Sunday - differences remain between the
GFS/EC deterministic guidance with respect to how a trough evolves
as it moves through the Pac NW into the northern Great Plains and
if/how another trough develops offshore. GFS and associated
ensembles suggest Arizona sees the influence of the offshore low
with warmer temperatures across the region. EC and ensembles depict
a much cooler system with Canadian cold air moving into the area.
Neither solution depict precipitation across southeast Arizona but
temperatures are up for debate. Will stick with a colder than normal
solution for now per the NBM.
&&
.AVIATION...Valid thru 19/00Z.
Cloud decks generally around 2-5k ft AGL with layers above thru
about 18/05Z, then increasing to 4-7k ft AGL from Tucson westward
with gradual clearing overnight. Areas east of KTUS will remain BKN-
OVC at 3-6k ft AGL into Monday. SCT valley SHRA and mountain SHSN
will continue into this evening, then gradually taper off overnight.
Some lingering valley SHRA and mountains SHSN is possible Monday
east of Tucson. MVFR cigs/vsbys will occasionally accompany the SHRA
especially near terrain and east of Tucson into this evening. Winds
mainly southeasterly at around 8 to 12 kts, though occasional gusts
to 25 kts may occur in/near stronger SHRA this afternoon, then
mainly less variable at 10 kts or less through Monday. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Low pressure will bring much higher relative
humidity and scattered precipitation to the area through Monday.
East to Southeast winds this afternoon will give way to relatively
light/diurnally driven winds during through midweek. Once the
current weather system moves to the east, expect dry weather the
remainder of the week. As a weather system approaches Thursday,
expect some increased breezes. The bulk of this system will pass to
our north, thus dry and cool weather to end the work week and into
next weekend.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM MST this evening for
AZZ510>514.
&&
$$
Leins/GL
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